1. Field of the Invention
The invention relates generally to methods and apparatus for drilling of wells, particularly wells for the production of petroleum products. More specifically, it relates to a drilling system with a non-rotating sleeve.
2. Background Art
When drilling oil and gas wells for the exploration and production of hydrocarbons, it is very often necessary to deviate the well from vertical and along a particular direction. This is called directional drilling. Directional drilling is used for, among other purposes, increasing the drainage of a particular well by, for example, forming deviated branch bores from a primary borehole. Also it is useful in the marine environment, wherein a single offshore production platform can reach several hydrocarbon reservoirs using a number of deviated wells that spread out in any direction from the production platform.
Directional drilling systems usually fall within two categories, classified by their mode of operation: push-the-bit and point-the-bit systems. Push-the-bit systems operate by pushing the drilling tool laterally on one side of the formation containing the well. Point-the-bit systems aim the drill bit to the desired direction therefore causing the deviation of the well as the bit drills the well's bottom.
The push-the-bit systems can utilize an external anti-rotation device or an internal anti-rotation mechanism. In the systems utilizing an internal anti-rotation mechanism the means for applying lateral force to the wellbore's side walls rotate with the drill collar. A push-the-bit system utilizing internal anti-rotation mechanism is described, for example, in U.S. Pat. No. 6,089,332 issued on Jul. 19, 2000 to Barr et al. This patent discloses a steerable rotary drilling system having a roll stabilized control unit with hydraulic actuators which position the shaft and steer the bit.
International patent application no. WO 00/57018 published on 28 Sep. 2000 by Weatherford/Lamb, Inc. also discloses a push-the bit system utilizing an external anti-rotation device. The system described therein is a rotary steerable system with a pad on a stabilizer activated to kick the side of the wellbore. The stabilizer is non-rotary and slides through the wellbore.
Push-the-bit systems utilizing external anti-rotation device may involve applying lateral force to the wellbore's side wall using systems de-coupled from drillstring rotation. For example, U.S. Pat. No. 6,206,108 issued to MacDonald et al. on Mar. 27, 2001 discloses a drilling system with adjustable stabilizers with pads to effect directional changes.
Various techniques have also been developed for point-the-bit systems. An example of a point-the-bit system utilizing an external anti-rotation device is disclosed in U.S. Pat. No. 6,244,361 issued to Comeau et al. on Jun. 12, 2001. This patent discloses a drilling direction control device including a shaft deflection assembly, a housing and a rotatable drilling shaft. The desired orientation is achieved by deflecting the drilling shaft. Other examples of point-the-bit systems utilizing external anti-rotation device are disclosed in U.K. Patent Nos. 2,172,324; 2,172,325 and 2,177,738 each to Douglas et al. The Douglas patents disclose that directional control is achieved by delivering fluid to an actuating means to manipulate the position of the drilling apparatus.
An example of a point-the-bit system utilizing internal anti-rotation mechanism is described in U.S. Pat. No. 5,113,953 issued on May 19, 1992 to Noble. This patent discloses a directional drilling apparatus with a bit coupled to a drill string through a universal joint which allows the bit to pivot relative to the string axis. The tool is provided with upper stabilizers having a maximum outside diameter substantially equal to the nominal bore diameter of the well being drilled and lower stabilizers having the same or slightly lesser diameter.
Despite the advancements of the steerable systems, there remains a need to further develop steerable drilling systems which can be utilized for three dimensional control of a borehole trajectory. It is desirable that such a system include, among others, one or more of the following: a simple and robust design concept; preferably without rotating oil/mud seals; and/or incorporating technology used in mud-lubricated bearing sections of positive displacement motors (PDMs) and/or variable gauge stabilizers. It is also desirable for such a system to include, among others, one or more of the following: a non-rotating stabilizer sleeve preferably de-coupled from drillstring rotation; a directional drilling and/or control mechanism actuated by drilling fluids and/or mud; a rotating section including active components such as electric drive, pumps, electric valves, sensors, and/or reduced electrical; and/or hydraulic connections between rotating and non-rotating parts. The present invention has been developed to achieve such a system.